It has become increasingly important to accurately space the insulated multiple conductors with respect to each other and laminated flat ribbon cable has increasingly come into use for this purpose. Precise control of electrical characteristics such as impedance, capacitance, cross talk and attenuation, especially important in digital data, and signal, transmission is thereby achieved. Both controlled regular spacing and controlled irregular spacing, of multiple conductors in ribbon cable form, has been achieved, in the prior art, by laminating the accurately spaced insulated (or uninsulated) multiple conductors between thin plastic film, such as 5 mil polyvinyl chloride (pvc) film or 5 mil polytetrafluoroethylene film.
Multiple pairs of insulated wires have also been accurately spaced, in ribbon cable, by laminating multiple pairs of twisted insulated conductors between plastic film, each individual twisted pair being first laid onto a lower plastic film and encapsulated and accurately oriented by an upper plastic film laminated to the lower film. The use of multiple twisted pairs in multi-conductor cable is of great importance in the field of communications, data processing and other applications where cross-talk in signal transmission must be kept to a minimum. The twisted pairs of the laminated, twisted pair, multi-conductor ribbon cable of the prior art are, however, difficult to separate and untwist from the laminate because each individual twisted pair is tightly encapsulated and/or bonded within the laminated film. More specifically, the conductors of each individual twisted pair are round, in cross-section, and the laminating plastic film readily conforms to the shape of the conductors during lamination under the influence of heat and pressure. Thus, even though each individual twisted pair is laterally separated from an adjacent individually encapsulated twisted pair, by an area, generally known as a "nip area" or a "bite area" in the art, it is nevertheless difficult to separate the individual twisted pair from the surrounding plastic film because of the tightly conforming nature of the plastic film to each individual twisted pair. For these reasons, it is time-consuming and costly to separate each twisted pair from the multi-conductor laminated cable of the prior art.
The invention is therefore directed towards an improved multi-conductor laminated cable, having a plurality of twisted pairs of cables laminated therein, in a unique manner, which overcomes the just-mentioned time consuming problems of separating and untwisting the cable for termination purposes without appreciably affecting the electrical characteristics if the cable, and furthermore improving the cable by having a narrower width for a given number of twisted pairs.